The Clinical Core will support multiple projects under the auspices of the proposed CTNA. The core will provide for oversight and coordination of subject recruitment and assessments. In addition, the core will be used to assist in the development of new assessments that may be included in future studies. The Clinical Core has three specific aims: 1) Centralized coordination of subject recruitment will occur in order to enhance the efficiency and rate of enrollment into each project, provide an avenue for referral among projects, and systematically monitor the effectiveness of different methods of recruitment. 2) Central oversight of assessment will occur in order to ensure that appropriate assessment are used, to provide efficiencies in training, and to insure that administration of assessments is standardized in all projects thereby enhancing the opportunity to pool data across studies. 3) The final aim is to support the development of new assessment methods in response to gaps in available methods and changing priorities in the filed. In this regard, the development of ligands to be employed in positron emission tomography (PET) and single photon emission computerized tomography (SPECT) is the single most critical step to applying neuroreceptors imaging to the study of alcoholism. This application has selected two receptor targets for ligand development based on the convergence of their importance to the field of alcoholism research and the feasibility suggested by existing chemical structures and/or related ligands: the human 5-HT-1B receptor and the glycineB site of the NMDA receptor.